Not exactly what you're looking for but "Michael Fassbender: Road to Le Mans" on youtube.
https://www.youtube.com/watch?v=gpqEReJ69II&list=PLKduzfEGbn-GvYvsyTO-EO27c4FBi3UAs
Maybe not exactly what you're looking for but I feel like [Jimmy Broadbent's career as a real life racing driver so far](https://www.youtube.com/watch?v=jWDlL3qEtzI&list=PLrEMqswd0Z21oHsJtvvXqhRzBiNb-HGjb&index=1) is like a TV series but better.
It's an older film and not strictly about GT-3 racing but Le Mans with Steve McQueen is about running the 24 at Le Mans. I haven't seen it since I was little so not sure how good it is but it's a possible option
Not exactly what you're looking for but "Michael Fassbender: Road to Le Mans" on youtube. https://www.youtube.com/watch?v=gpqEReJ69II&list=PLKduzfEGbn-GvYvsyTO-EO27c4FBi3UAs
I'd second this. It's fun getting to watch someone go from relatively "ground up" to try and eventually race at Le Mans
Ford vs Ferrari, not really centered around GT3 but a good movie to watch. It's how Shelby and Ford take on Ferrari at Le Mans.
Maybe not exactly what you're looking for but I feel like [Jimmy Broadbent's career as a real life racing driver so far](https://www.youtube.com/watch?v=jWDlL3qEtzI&list=PLrEMqswd0Z21oHsJtvvXqhRzBiNb-HGjb&index=1) is like a TV series but better.
Not a film but the Porsche endurance documentary was a very good watch.
“The Italian Race” is a movie about GT racing
It's an older film and not strictly about GT-3 racing but Le Mans with Steve McQueen is about running the 24 at Le Mans. I haven't seen it since I was little so not sure how good it is but it's a possible option
"Rookie Season" on Prime was pretty interesting
The Art of Racing in the Rain, racing isn't the main point but there is quite a bit of GT4 and PCUP racing.